DESCRIPTION: Periodontitis is a chronic inflammatory response to bacterial pathogens that causes damage to both bone and soft tissues that support the teeth. Extensive effort has identified the genes for relatively few bacterial antigens related to periodontitis. Therefore, the host immune response to oral bacteria during periodontal disease has not been adequately characterized. Analysis of the molecular interactions that occur between oral bacteria and host cells is a high priority of NIDCR, and will contribute to our basic understanding and clinical tools for periodontal disease. The overall goal of this project is to define the bacterial proteins (antigens) that elicit humoral immune responses during periodontal disease, and determine how the different antibody specificities relate to the severity of disease, or response to treatment. Our hypothesis is that the presence of antibodies to certain groups of bacterial antigens is associated with the severity of periodontal disease or the response to treatment in patients. To address this hypothesis, we propose to use bacterial genomic DMA to create bacteriophage lambda expression libraries for Porphyromonas gingivalis, and Actinobacillus actinomycetemcomitans. We will screen the libraries with periodontitis patient and control sera to identify antigenic peptides. The antigenic proteins will be arrayed on microarray slides and screened with individual patient serum. The presence of specific antibodies, or groups of antibodies, will be related to the clinical indices of the patient using hierarchical cluster analyses. This approach takes advantage of the extremely high gene density of the bacterial genome, which lacks introns, and of the technological advances for construction of microarrays. The R21 Exploratory Grant is an appropriate mechanism since proteomics have not been used for periodontal disease, and bacterial genomic expression libraries and antigen microarrays need to be developed. [unreadable] [unreadable]